(a) Field of the Invention
The present invention relates to a method for preparing polyacrylonitrile-based polymer using microwave and melt-spinning it to prepare carbon fibers.
(b) Description of the Related Art
Carbon fiber, lighter but stronger than steel, has been widely used in a variety of applications, such as automobile, aircrafts, aerospace, sports, and so forth.
For example, as the recent environmental concerns have led to tightened restrictions on vehicle emissions and an increase in demand for high fuel efficiency, light-weighted vehicles, the technique of using carbon fiber reinforced composites is noted as a solution to reduce the weight of vehicles at no expense for structural and mechanical strengths.
Carbon fiber is, however, far too expensive for its applications and commercialization, so there has been a pressing need for developing techniques for mass production of high-performance carbon fibers at low cost.
Based on precursor fiber materials, the carbon fiber is classified into polyacrylonitrile-based carbon fiber, rayon-based carbon fiber, and pitch-based carbon fiber.
The techniques of preparing precursor fibers for carbon fiber are wet spinning, dry spinning, and melt spinning, among which the melt spinning technique is a fast spinning method requiring relatively simple facility and low cost without a need for collecting a solvent or a solidified solution.
To prepare precursor fibers using the melt spinning technique, the polyacrylonitrile-based polymer is required to have thermoplasticity and a melting point for spinning lower than the stabilization temperature. For enhanced efficiency of the preparation process for carbon fibers, there has been suggested a method of reducing the production time of polyacrylonitrile-based polymers using a plurality of polymerization reactors connected to one another in series or parallel, which problematically increases the yield of byproducts and degradation products to deteriorate the whole production efficiency.
Hence, there is a pressing demand for developing a technique to prepare polyacrylonitrile-based polymers having properties adequate to preparation of carbon fibers using a simplified method at low cost.